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Mate there used to be a manufacturer (KAM, I think) who did an ATB guts in a diff with also selectable full locking - for front/rear diff. Just like the Ashcroft ATB replacement for the Defender centre diff, it is still fully lockable. Best of both worlds.Quote:
Originally Posted by ozscott
Well done on starting a specific thread.......although near impossible to keep on track. Certainly some good information.Quote:
Originally Posted by tact
Maybe it could be cleaned up and transferred to the good oil
In my previous car (very modified Great Wall X240) I had a Detroit auto locker in the rear and a torsen type locker in the front. The front locker was made in Russia, and I am sure Jacden, member on this site can give you details. The front locker when in 4wd was not really noticable in forward motion. However it was almost impossible to steer the car in the following situation. When in reverse and going up a hill, Ie under load, steering was extreemly hard. So much so that the only way to steer was to back off the speed and then turn the wheel at the same time. The thing I liked about my lockers were that no one knew you had them, and there was no need to guess or anticipate do I need to have the lockers on? As a result, in just about every sticky situation, I would get up or get through first try, whilst others with manual lockers, would have to suddenly realise oh **** I need my locker on and try to quickly fumble for the switches etc. Around town the rear locker would sometimes get wind up and then there would be a "clunk" noise as it released the wind up. After a while you just got used to it and no damage or bits of metal were ever detected in the diff oil when it was replaced.
Not an ATB style diff, a plate type LSD.Quote:
Originally Posted by tact
Wave Trac in the US make an ATB type diff with pre load springs (belville washers) on the helical gears, this helps torque biasing if you lift a wheel.
No, they don't make them for Rover diffs, they are aimed at motorsport, e.g. a Mustang lifting an inside wheel coming off a corner on the track.
Ashcroft's ATB has more inherent pre load and a 'better' bias ratio than the TruTrac, not sure re the Quaife.
As I've mentioned previously, aggressive TC is the perfect accompaniment to an ATB style diff, allowing it to do its thing and bias torque if one wheel loses traction.
Having said that, I'm **** with TC!
I'm still so old school, if a wheel starts to slip and spin I'm modulating the throttle, searching for grip instead of hammering the loud pedal and letting the electrickery do its thing!
I do the same with ABS, I used to out modulate the ABS in the work BT50 and do the same with the current Hilux!
I had the inside front Michelin howling it's displeasure without triggering the ABS conning into a corner last week. [emoji23]
Quote:
A good read at the torsen site.
Quote:
"Torsen® differentials are torque-biasing, meaning they distribute torque between the tires – biasing more torque toward wherever it’s best used – without requiring a loss of traction to operate."
Just checking I have not misunderstood - Have I got the right incredibly correct quote to which you refer? (above)Quote:
Originally Posted by Slunnie
It thats the quote then we agree here for sure. That a loss of traction is not needed for ATB's to operate.
(lets hold very loosely, for a paragraph or two yet to come, whether differing rotational speeds across an ATB (e.g. cornering) isn't any different to a slipping wheel - from the ATB's perspective)
Errrm... you might be reading something a bit more than intended into my assertion that the ATB is pre-emptive, i.e. it is already set to resist differentiation even while traveling in a straight line.Quote:
Originally Posted by Slunnie
Am happy to agree with you that while traveling in a straight line, where a 50/50 torque split is naturally in play whether there is an ATB or open diff present - no torque "biassing" is happening at that point.
There is another situation where there is near enough to zero torque biassing happening with an ATB - thats when a wheel is lifted, or when cross axled. (ignoring small amounts of preload) essentially there is no torque torque to bias so no torque biassing in play.
So no argument from me about whether an ATB is doing any biassing when there is no torque to bias, or when the cross axle loading is 50/50.
What i am trying to explain (the preemptive thing) is that with an ATB in play: At any time there is load on the driveline, including when traveling in a straight line with a nice 50/50 torque split, the ATB will be predisposed to resist any differentiation.
(Recall the image of the strap on on the pin with a bit of load on it... can't twist the pin, can't pull it out....)
Call it "onroad situational realtime dynamic preloading (OSRDB) of the ATB" if you want, no need to call it "biassing".
Further - I am positing that when the likes of Torsen, in the quote I think you have written is "incredibly correct" where they write "– without requiring a loss of traction to operate.", are saying the same thing.
The data I have seen in the past for Bias ratio if I recall correctly is:Quote:
Originally Posted by rick130
Trutrac 3.5:1
Ashcroft 3:1
I think I have read perhaps in Ashcrofts information something that would lead you (or rather me!) to think the Trutrac is 2:1, but thats not actually the case, it is actually more positive than the Ashcroft.
Having read on the torsen website that they can have varying degrees of bias with power on and power off(they list the specs as drive/coast using the term TBR).
I'm curious what the Ashcroft bias for both drive/coast is .. or if it's the same.
eg. the Torsen Dana 44 T-2R has a TBR of 4:1/3:1 drive/coast, whereas the same specs for non R version are listed as 2.1/2.3 .. which I assume is 2.1:1/2.3:1
Good e.g. of being able to get the power down with Truetracs.
Range Rover V8 **Eaton No-spin/truetrac Lockers-38.5/11.5/16** - YouTube
Cheers
Ta, I thought it was the other way around too.Quote:
Originally Posted by Slunnie
Just gone back through some old posts hoping Ian and Dave divulged bias ratios but alas......
Here we are, I thought it would be good to check what I thought I know:Quote:
Originally Posted by rick130
Ashcroft ATB 3:1
Ashcroft Transmissions
Quote:
One of the drawbacks of the ATB is that it is always necessary to have some load on one wheel per axle. if there a no load situation eg cross axle the wheel with traction would only see approx three times the load on the wheel with no traction ie nothing!!. To overcome this, as stated earlier, the ATB is fitted with some preload springs to provide some loading to the side with no traction in the event of a cross axle, where this pre-load is not providing sufficient traction to the other side then one favourite trick is to apply a small amount of left foot brake whilst applying more throttle. This manouver fools the diff by providing load to the non-traction side which is multiplied by the ATB (approx 3:1) to the other side, the loss of drive attributed to the brakes which are acting equally on both wheels is overcome by the additional throttle. In a car fitted with Automatic Traction Control this braking all takes effect automatically and the ATB provides additional traction by multiplying the ATC effect.
Quaife ATB 2:1
Quaife will not comment generally as they don't see any value in it.
But did directlyQuote:
Quaife does not specify bias ratio details and generally, does not use the term. The Quaife ATB differential is an all helical gear design. The angle and tooth form of the helix used, the number of pinions used and many other factors (including the individual vehicle application in question) all contribute to how the differential behaves and biases drive torque across an axle. Each Quaife ATB differential application is designed to offer the best compromise between performance and durability, which is why it is regarded as the industry benchmark design.
Torsen vs. Quaife - Bias ratio (REAL answer in here!)!)
and this is supported by Ashcroft transmissionsQuote:
Originally Posted by Quaife We do not use or quote TBR figures as they don't really mean much to anyone. The TBR is a very difficult thing to measure (we know this from our work with OEM diffs) and actually not very useful.
Essentially the TBR is a complicated way of comparing the helix angle of the internals (sun gears and pinions) and the vast majority of our diffs have the same angle internals although some of the very large and very small diffs have different angles. A few diffs have options (eg QDF9U) as they are used in different applications, i.e. QDF9U (31dg) in a Honda Civic Type R or QDF9U/23dg in an Ariel Atom. If you put a standard QDF9U (31dg) in an Atom (very light mid engined car) the diff would push too hard for the amount of grip at the front.
Now i have explained my position, the answer to your question is around 2.1 on drive and 1.9 on coast (for a 31dg diff which is most of them). These figures were measured and produced by Getrag Ford using the new Focus RS diff which is a modified M66 gearbox (QDF13J).
The 3 diffs you have listed are all 31dg. Good luck
Ashcroft Transmissions
Quote:
The diff is fitted with sets of "helical" gears sitting in pockets within the diff, the helical gears are unsupported so as they work together they generate friction against the sides of the pockets, the amount of friction is determined by the helix angle and preload on the gearset. In a situation where one wheel has less grip than the other there is a tendancy for this wheel to spin. Due to the friction within the internal gearset and the configuration of the gears the wheel which has retained grip can still drive "but" the torque transmitted to the "driver" will be proportional to the torque transmitted by the "slipper" this is the ATB effect and can be up to 2:1 ratio.
Detroit Trutrac 3.5:1
Detroit Trutrac Differential, Helical Gear Limited Slip Differential - Vehicle - Eaton
http://www.eaton.com/ecm/idcplg?IdcS...me=PCT_1629018
Quote:
The Truetrac performs like an open differential under normal conditions, and automatically transfers torque to the wheel with the highest traction when required. The Truetrac can transfer up to 3.5 times more torque to the high traction wheel. This torque transfer ratio (called the bias ratio) is accomplished by using helical side gears and pinions. The bias ratio is the result of pressure exerted by the side gears and pinions against the surface of the differential case. In certain applications, this normal gear engagement may produce temporary driver feedback.
Torsen 2:1-4:1... There is so little info on LR fitments!
https://torsen.com/faq/
Quote:
In general, the TBR level of Type-2 products is between 2:1 and 2.5:1, whereas T-2R models are in the 3:1 to 4:1 range. This varies depending on the specific model. The TBR level of Type-1 differentials can be anywhere from 2.8:1 to 4:1, depending on the design requirements.